Study On Structure Design And Flatness Metrology Method Of Mosaic CCDs For Large Aperture And Wild-field View Telescope

In order to satisfy the increasing curiosity and exploration ability of mankind to the universe,the imaging quality and resolution of the telescope have been improved day by day.With the increase of the aperture of the telescope,in order to meet the imaging requirements of the large-aperture and wide-field-of-view telescope,it is necessary to splice several CCD on the focal plane of the camera so that the area of the CCD can cover the full-field of view of the telescope to meet the imaging requirements,it has become the focus of the camera design of large aperture and wide field of view(Fov)telescope.Large aperture means the depth of field of the optical system is small,and large field of view means the area of the camera target.Summarize the key problems to be solved in this paper,the main research contents for the design requirements are as follows.This paper summarizes the latest research progress of the measurement methods of target flatness for large-aperture and wide-field-of-view(Fov)optical telescopes at home and abroad,and from the point of view of the characteristics of target surface splicing and measuring methods and equipment,several widely used methods for measuring the flatness of target surface are compared,a method for measuring the flatness of the splicing target is presented.In view of the cost,measurement accuracy and analysis system,the color laser confocal measuring instrument was adopted,and the high precision gantry platform and operating system were used,a set of more convenient and fast optical measurement system with higher measurement stability has been built,and the evaluation standard of flatness result only for this paper has been set up,the measurement results obtained by this method are evaluated to meet the imaging requirements of the optical system.This paper describes the design and integration process of the spliced detector,and obtains the technical indexes of the spliced target surface based on the national standards,including the simulation drawing of the splicing prototype design,the design and installation method,and the assembly simulation drawing,the window design,the temperature control,the vacuum seal and the vacuum penetration of the dewar in the camera are discussed,to ensure that the structure meets the design criteria and can provide the experimental basis for the flatness measurement of the splice target surface.According to the Monte Carlo method model,the mathematical model of the minimum conditional error evaluation is selected,and the method of calculating the flatness error under the least squares model is obtained According to the uncertainty model of Gum,the source of uncertainty of measurement is analyzed,and the formula of uncertainty of synthetic flatness is obtained,the transfer coefficients of the uncertain inputs are calculated.The Verification Test of the system measurement accuracy is carried out.In the same measurement environment,for the same measurement target,the interferometer measurement results are selected as a contrast reference to verify the correctness of the optical measurement system,the process can be used for testing and setting up the real detector in the later period.Finally,the CCD is measured at normal temperature and in vacuum cooling environment,in addition,the measurement method and the measurement result can not be affected by the window and the measurement distance,the measurement result is analyzed with error,the measurement result is processed with Matlab,and the fitting equation of CCD plane and the surface shape feature are obtained,the flatness result evaluation standard is used to determine whether the measured result meets the requirement.The measurement method proposed in this paper can not only meet the requirements of high-precision non-contact measurement of planarity,but also has obvious advantages over interferometer in the measurement of planarity of groundbased large-aperture large-field-of-view telescope detector,it also provides some experience for the measurement of flatness of the focal plane splice detector of the ground-based large aperture and wide field-of-view telescope.